Sunday, July 3, 2011

Change your diet, change your microbes?

In this week's issue of Science, an interesting article by Faith et al. at Wash U in St. Louis described the effects of dietary changes on the composition of gut microbes in a "human gut" mouse model. Ten strains of human gut bacteria were introduced into mice that had few (or no) gut microbes of their own to mimic the effects of dietary changes on the human gut. The authors could predict the changes that occur in gut microbe compositions after changing the mouse diets in specific ways. Because different microbes play different roles in nutrient utilization and overall health, the results suggest that very real changes in your ability to use the nutrients in your food could be made by changing the composition of your diet.

The researchers changed the proportions of protein, fat, carbohydrate and sugar of the mouse diet and looked at the overall numbers and percentages of the ten human gut species in the mouse guts. Higher levels of protein led to higher overall numbers of microbes. Seven species (including E. coli) had increased numbers with increasing protein percentage, while the other three had decreased numbers. It wasn't clear why these three species had decreased numbers, but the authors suggest that it could be an effect of simple competition for resources. Changing the concentration of fat had no significant effect on any individual species or overall microbe numbers, and carbohydrate and simple sugar concentrations only had effects on one species each. So... the main factor that affects the microbe composition in your gut seems to be the concentration of protein in your diet.

Studies like this could be useful on many levels. Knowledge of how diet can affect normal microbial loads in people's guts can help to develop food programs for poor and undernourished people. It can also help to make specific dietary recommendations for different life stages. Also, and this is my personal speculation, this information could be helpful for people with severe food allergies who want to plan optimal diets but have restricted food choices.

The study has a lot of moving parts and much more information than I have space to talk about, but if you're interested in the topic, the Gordon lab is doing fascinating work on this topic. I don't think any recommendations for human diets can be made yet, but this is an important step toward understanding how diet can relate to and affect gastrointestinal microbial communities.


Faith JJ, McNulty NP, Rey FE, Gordon JI. Predicting a human gut microbiota's response to diet in gnotobiotic mice. Science. 2011 Jul 1;333(6038):101-4.

Gordon Lab at Washington University in St. Louis School of Medicine;